• Journal of Biosystems Engineering
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• v.13 no.4
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• pp.38-45
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• 1988

The freeze drying of garlic juice was carried out in a vacuum freeze dryer, laboratory size, by backface heating. The factors which influence the rate of freeze drying, the pressure of drying chamber, the plate temperature, the concentration and the thickness of a sample, were discussed in this study. The drying rate was in proportion to the drying chamber pressure and when the pressure was at 1.5 torr, the foaming occured on the surface of materials, so this condition was not suitable for freeze drying. As the temperature of plate increased, drying rate increased, but when the temperature was $20^{\circ}C$, it was impossible to accomplish freeze drying because the foaming and the dispersion occured in a sample. The higher the concentration of a sample was, the lower drying rate was.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.2
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• pp.386-391
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• 2004

This study was performed to investigate change of quality characteristics on traditional dried Persimmons from Sangju varity regions (sun-dried, Namjang and Bokryong). Moisture contents on drying were decreased and constant at from 7th to 14th days drying periods and its periods were recognized to constructing second peel of dried persimmons. Constructed second peel were affected on quality characteristics of traditional dried Persimmons. Also, in case of semi-dried persimmons were processed at 45∼55% level of moisture content. Final products of semi -dried persimmons were estimated in 25th from initial drying periods. Changes of water activity were increased reducing speed at time of water content decreased, second feel constructing during drying persimmons were introduced to decreasing of water activity. Weights of dried Persimmons were quickly decreased in 21th drying periods and slowly decreased after that time. Weight changing and water evaporation of dried persimmons at the Namjang and Bokryong were slowy decreased and controled after 7∼14th in periods of constructing second feel of dried persimmons. Change of brix in dried persimmons have had in 18∼27% value at initial drying periods and quickly increased after 7∼14th in drying periods and have in high value of 40∼50% at 21th drying periods. At the texture of dried persimmons, hardness were decresed after 7∼14th in periods and effected on decreasing of water content, increasing of drying times. Sensory score of dried persimmons were highest score of color, sweetness and texture at dried persimmons of Namjang. Score of astringency, sourness and mold smell were highest at dried persimmons of Bokryong. Value of highest overall acceptance score was at dried Persimmons of Namjang.

• Food Science and Preservation
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• v.23 no.5
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• pp.689-695
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• 2016

In this study, the drying characteristics of medicinal (Ganoderma lucidum, Phellinus linteus) and edible (Pleurotus eryngii, Lentinus edodes) mushrooms were investigated. Their shrinkage ratios, Hunter's color values, and rehydration ratios were evaluated. Mushrooms were cut with rectangular (1 cm) and square ($1{\times}1cm$) shapes, and dried in the room temperature and at $50^{\circ}C$ and $70^{\circ}C$ using hot-air dryer. Initial moisture contents of edible mushrooms were higher than those of medicinal mushrooms, whereas final moisture contents were vice versa. Drying rate was the highest when drying at $70^{\circ}C$ (p<0.05). Moreover the drying rate of square slices was higher than that of rectangular slices (p<0.05). The shrinkage ratios of both medicinal mushrooms and edible mushrooms were the least when drying at $50^{\circ}C$ and $70^{\circ}C$, respectively (p<0.05). The changes of color values were less in the medicinal mushrooms dried in the room temperature than in the hot-air dried medicinal mushrooms (p<0.05). However, in case of edible mushrooms, the changes of color values were less in the hot-air dried mushrooms (p<0.05). Rehydration ratios of medicinal mushrooms dried at $50^{\circ}C$ was the highest (p<0.05). In contrast, rehydration ratios of edible mushrooms was the highest when drying in the room temperature (p<0.05). Thus, the hot-air drying at $50^{\circ}C$ would be suggested as the efficient drying method for both medicinal mushrooms and edible mushrooms.

• Food Science and Preservation
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• v.16 no.6
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• pp.797-803
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• 2009

The effects of drying methods on the browning and moisture sorption characteristics of Rubus coreanus were studied. Fruits were steamed for 5 min at $100^{\circ}C$, dried by sun drying, infrared drying, or freeze drying, and powdered to a size of 20 mesh. Color values were measured and equilibrium moisture contents (EMC) were determined at $20^{\circ}C$, over a range of water activity ($a_w$) from 0.11 to 0.90. The browning indices $L^*$ and $a^*$ values were higher and lower, respectively, in freeze-dried Rubus coreanus compared with other samples. The $b^*$ value was greatest in freeze-dried Rubus coreanus. EMC tended to increase with increasing $a_w$ values, and a particularly sharp increment was observed above 0.75 $a_w$. The EMC of freeze-dried Rubus coreanus was significantly higher compared with the EMC of sun-dried and infrared-dried fruit at constant aw. The moisture sorption isotherms showed a typical sigmoid shape, and the Halsey, Kuhn, and Oswin models were the best fits for the sun-dried, infrared-dried, and freeze-dried powder isotherms, respectively. With respect to monolayer moisture content, the Guggenheim-Anderson-Boer (GAB) equation showed that the various drying methods yielded very different results, with monolayer moisture contents of 0.005 g $H_2O/g$ dry solid in infrared-dried and 0.019 g $H_2O/g$ dry solid in sun- and freeze-dried powders, respectively. These results indicate that the drying method affects the browning and moisture sorption characteristics of Rubus coreanus.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.9
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• pp.1320-1325
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• 2012

This study investigated the bulk properties of red pepper powders according to drying method and variety. Bulk density, compressive characteristics, irrecoverable work, dynamic angle, and stress relaxation were investigated. Loose bulk density ranged between 0.420 $g/cm^3$ for Cheongyang cultivar and 0.427 $g/cm^3$ for Hanbando cultivar by hot-air drying. The highest tapped bulk density was 0.586 $g/cm^3$ for Hanbando cultivar by far-infrared drying and the lowest value was 0.523 $g/cm^3$ for Hanbando cultivar by sun drying. Hausner ratio reached a maximum value of 1.370 for Hanbando cultivar by far-infrared drying. Compressibility ranged between 0.0016 for Cheongyang cultivar by sun drying and 0.0023 for Hanbando cultivar by far-infrared drying. Compression ratio reached a maximum value of 1.032 for Hanbando cultivar by hot-air drying. Dynamic angle of repose ranged between 37.47 and $42.97^{\circ}$. Irrecoverable work ranged between 76.0 and 81.7%. Relaxation reached a maximum value of 24.31% for Cheongyang cultivar by far-infrared drying.

• Korean Journal of Food Science and Technology
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• v.42 no.1
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• pp.45-49
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• 2010

To reduce the astringent taste of lotus root, the effects of various treatment methods such as drying, soaking, steaming and roasting on the physicochemical properties and sensory characteristics were investigated. The following process conditions were selected: 1) drying (D), 2) soaking followed by drying ($SK{\rightarrow}D$), 3) steaming followed by drying ($ST{\rightarrow}D$), 4) drying followed by roasting ($D{\rightarrow}R$), 5) soaking and then drying followed by roasting ($SK{\rightarrow}D{\rightarrow}R$), 6) steaming and then drying followed by roasting ($ST{\rightarrow}D{\rightarrow$}. The tannin content of the lotus root was lowest when it was treated by steaming followed by drying ($ST{\rightarrow}D$). The astringent taste of lotus root was reduced by steaming, and the roasted taste was improved by roasting in terms of sensory and flavor characteristics. Consequently, lotus root treated by steaming and then drying followed by roasting ($ST{\rightarrow}D{\rightarrow}R$) showed the highest preference with respect to astringent and roasted taste.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.706-713
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• 2001

The influencing factor in drying characteristics of fluidized bed drying with different drying conditions for husked barley were carried out. This fluidized drying mechanism of husked barley was consisted of consecutive two falling rate parts, first falling rate period and second falling rate period without showing constant rate period. The drying rate constant was increased with decreasing charged amount and relative humidity and increasing air temperature and air velocity. Since the drying rate constant expressed by Arrhenius type equation in the falling rate period showed good linearity, the falling rate period was condsidered as the controlling step. The activation energy of first falling step was 1,100 cal/gmol, while for second falling step the values showed 1,600 cal/gmol.

• 한국문화재보존과학회:학술대회논문집
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• 2004.10a
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• pp.115-130
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• 2004

Plant-based cultural assets using straw and grass as household goods of our people's have been used as indispensable tools for practical living for a very long time. However, only a limited number of artifacts were unearthed so far due to tile fragility of the material. For this reason, research on plant-based cultural properties had close to no progress, and the appropriateness of the PEG method, high-grade alcohol method, alcohol--ether-resin method, and Paraloid B-72 used in preserving plant-based cultural properties has not been sufficiently investigated. Therefore, this study examined the weight change rate by applying the methods of Primal MC-76 and vacuum freeze-drying used mostly as a earth-layer hardening material among PEG and acrylic resin, which are applied widely for preservation of waterlogged archaeological wood, as a means to preserve plant-based cultural properties along with the examination of the subject material, and an experiment was also performed on moisture absorption. The findings as a result were, first, the plant-based material being studied was found to be Typha (Typha orientalis Presl). Secondly, the weight change experiment applying $PEG\#400$ and $PEG\#4000$ confirmed a steady increase of weight if PEG -2Step is used for treatment. Third, in preserving all subject materials with soil, treatment with $PEG\#4000$, Primal MC-76, and vacuum freeze-drying showed that tile vacuum freeze-drying method resulted in the largest or $20\%$ reduction in weight, while Primal MC-76 resulted in $18\%$ and $PEG\#4000$ in $8\%$ of weight reduction. It was concluded that, considering the stability of soil measurement, this came to be because resin permeation was carried out along with tile drying process. Fourth, the weight changes were found to be around $10\%$ in various humidity conditions after the preservation treatment. The greatest weight change rate was seen in the case of $PEG\#4000$, particularly having chemicals gush out in a high humidity (RH $84\%$ or higher) environment. In the case of Primal MC-76 and vacuum freeze-drying methods, $6\~8\%$ weight changes were detected, and the lowest weight change was found in the case of the vacuum freeze-drying method. Fifth, as for color changes after treatment, blackening occurred most strongly with $PEG\#4000$, while Primal MC-76 and vacuum freeze-drying manifested colors closest to dry straw or grass. However, the texture of straw was not very evident in the case of Primal MC-76, due to a glossy surface, but vacuum freeze-drying was found to offer tile best result in terms of texture. Putting together the results of the above experiments, vacuum freeze-drying presented after being treated with PEG2-Step the most stabilized changes in weight, while it offered the smallest change in color as well.

• Korean Journal of Food Science and Technology
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• v.21 no.5
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• pp.676-685
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• 1989

Optimal operating conditions of on-farm red pepper dryer were searched by using the simulation-optimization algorithm combining the drying and quality deterioration models of red pepper with Box's complex method. Determination of control variables such as air temperature, air recycle ratio and air flow rate was based on a criterion of minimizing energy consumption under the constrainst conditions that satisfied the specified color retention of carotenoids. As quality constraint was stricter, energy consumption increased and total drying time decreased with lower recycle ratio and higher air flow rate Product mixing during drying was found to be able to improve the energy efficiency and product quality. Currently used air flow rate was assessed to be increased for the optimal operation. Two stage drying at the fixed optimal air flow rate was proven to be useful means for further saying of energy consumption. In the optimal bistaged drying, the second stage began at about one third of the total drying time and low air temperature in the first stage Increased to a high value and air recycle ratio increased slightly in the second stage. Optimal control variable scheme could be explained by the dryer performance and the carotenoids destruction kinetics in red pepper drying.

• Korean Journal of Environmental Agriculture
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• v.13 no.2
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• pp.223-230
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• 1994

A practical study on a drying and fermentation system equipped with a stirring machine operated mechanically, of pig manure was conducted to prove the efficiency of and practicability to an ordinary pig farm. The type of the drying bed was a round-shaped (r=3m) concrete structure and the stirring machine was adopted to stir and transfer dried pig manure to the fermentation tank. The dried pig manure was put into a fermentation tank ($V=18m^3$), which was aerated from pipe lines installed at the bottom. While water content of pig manure passing through a drying bed was remarkably reduced than before drying, the drying efficiency of this system decreased in winter. However, the temperature of pig manure piled up in the fermentation room in winter reached over $60^{\circ}C$ and excess water of pig manure was removed during the fermentation process. The reduction rate of water content of pig manure, to which dried pig manure was added as bulking material on the drying bed, was 52.1%, but when dried without bulking material it was only 19.7%. Although the content of $P_2O_5$ of dried pig manure was slightly higher than that of fresh pig manure, progressive changes in chemical composition between fresh and dried pig manure made no great difference. Among the contents of minerals of fresh and dried pig manure, CaO was the highest and the rest were in the decreasing order of $K_2O$, MgO, and $Na_2O$. Population density of E. coli and Streptococci of dried pig manure was reduced by 142 and 236 times that of fresh pig manure, respectively. The installation cost of this drying and fermentation system was 4,185,630 won (approximately 5,232 US $) and operating cost per year was 190,000 won (237.5US $) on the basis of self-labor condition.